Injection Moulding

Question 1

Injection Moulding - What are the 3 zones of the screw?

Answer 1

Feed zone
Melt zone
Metering zone

Question 2

Injection Moulding - Describe the feed zone of the screw

Answer 2

Half of the screw

Constant flight depth which forces the material together and rids it of air

Question 3

Injection Moulding - Describe the melt zone of the screw

Answer 3

Decreasing flight depth, reduces plastic volume

Causes plastic molecules to rub harder together, plasticising the material

Question 4

Injection Moulding - Describe the metering zone of the screw

Answer 4

Constant flight depth, much smaller than the feed zone.

Acts as a pump

Question 5

Injection Moulding - What causes a build-up in plastic?

Answer 5

The force of the plasticised material pushes the screw back as it turns, building a chamber of plastic in front of the screw.

Question 6

Injection Moulding - How is the molten material injected?

Answer 6

When enough material for the injection shot is melted, the screw stops and pulls back to decompress the material. For injecting the material, the one-way valve on the tip is closed as the screw is hydraulically pushed forward by the injection cylinder. This sends the molten material through the injection units nozzle and into the injection mould.